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Fundamentals of Medicine > infection and microorganisms > Flashcards

infection and microorganisms Flashcards

(54 cards)

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1
Q

name the four human pathogens

A
  • viruses
  • bacteria
  • fungi
  • parasites
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2
Q

name the two types of parasites

A
  • endoparasites

- ektoparasites

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3
Q

give examples of endoparasites

A
  • protozoa
  • parasitic worms
  • flukes
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4
Q

what size are viruses?

A

18-300 nm

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5
Q

describe the key structures of viruses

A
  • capsid (virus-encoded)

- outer cell-membrane (host derived)

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6
Q

describe viral nucleic acid

A
  • 3-300 Kb
  • DNA/RNA
  • single or double stranded
  • circular or linear
  • continuous or segmented
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7
Q

describe viral structural proteins

A
  • determine symmetry (and virus structure)
  • protect the nucleic acid
  • play a role in target cell infection
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8
Q

describe viral enzymes

A
  • often carried in virus particles to enable viral nucleic acid replication
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9
Q

describe viral glycoproteins

A
  • inserted into envelope

- play a role in host/target cell infection

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10
Q

name the three types of viral symmetry

A
  • icosahedral
  • helical
  • complex
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11
Q

give an example of an icosahedral/cubical structure

A

herpesvirus

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12
Q

give an example of a helical virus

A

influenza A

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13
Q

give an example of a complex virus

A

poxvirus

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14
Q

what determines the symmetry of a virus?

A

virus structural proteins, arranged as morphological units called capsomeres

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15
Q

how are viruses classified?

A
  • type of nucleic acid (DNA/RNA)
  • sequence of nucleic acid
  • number, ss/ds and polarity of nucleic acid strands
  • particle size, structure and symmetry
  • mode of replication
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16
Q

name the three methods of virus propagation

A
  • in vitro cell culture
  • embryonated eggs
  • animal models
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17
Q

describe in-vitro cell culture

A
  • primary cell lines

- continuous cell lines

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18
Q

describe primary cell lines

A
  • derived from healthy tissue

- finite number of cell divisions

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19
Q

describe continuous cell lines

A
  • transformed/immortalised cells

- infinite number of cell divisions

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20
Q

describe the use of embryonated eggs

A
  • amniotic fluid (influenza A)

- chorio-allantoic membranes

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21
Q

describe propagation using animal models

A

suckling mice (eg. neurotropic viruses such as poliovirus)

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22
Q

describe different methods of viral introduction to the body

Study These Flashcards
A
  • oral transmission
  • droplet
  • direct inoculation
  • direct skin contact
  • trans-placental
  • sexual transmission
23
Q

describe viral entry into cells

Study These Flashcards
A
  • attachment of virus to host receptor
  • penetration
  • uncoating (capsid is shed)
  • replication
  • assembly (capsids form around nucleic acid)
  • release (by budding forming envelope/exocytosis)
24
Q

how does a virus penetrate a host cell?

Study These Flashcards
A
  • receptor-mediated endocytosis

- fusion

25
how does a virus leave the host?
- budding to form envelope | - exocytosis if no envelope present
26
describe viral replication
- synthesis of viral mRNA - synthesis of viral protein for new capsids - synthesis of viral nucleic acid
27
how is ss retro RNA transcribed
RNA --> DNA/RNA (ds) --> transcription
28
what are the early viral proteins used for?
- non-structural proteins | - enzymes, regulatory molecules for replication
29
what are the late proteins used for?
- structural proteins | - formation of capsid
30
how is ss- replication different from ss +?
need to first produce + strand of RNA
31
how is viral replication different between RNA/DNA?
- DNA viruses replicate their genome in the NUCLEUS | - RNA viruses replicate their genome in the CYTOSOL
32
describe budding of viruses
- glycoproteins synthesised by mRNA and inserted into the host plasma membrane - matrix proteins are synthesised by viral mRNA. They form part of the envelope - modified region extends off and is budded from the plasma membrane - modified region encloses the viral matrix protein and RNA within the capsid
33
describe egress by cytolysis
cell destruction | causes a cytopathic effect (CPE)
34
name a function of CPE
diagnostic virology (virus detection in tisse culture)
35
give the outcomes of viral infection
- acute lytic infection - persistent infection with shedding - latent infection with reactivation - persistent slow infection with or without acute stage - transformation
36
what is an acute lytic infection?
- virus replication and release of virus progeny via cell lysis
37
give examples of acute lytic infections
poliovirus | influenza A
38
describe 'persistent infection with shedding'
virus persists in cell and replicates slowly
39
give examples of 'persistent infection with shedding'
hep B
40
describe 'latent infection with reactivation'
- virus persists in cell but is quiescent - disruption of latency triggers reactivation - genetic material may persist in host cell nucleus
41
give an example of 'latent infection with reactivation'
herpes
42
what is an episome?
genetic material remains in host cell nucleus
43
describe 'persistent slow infection with/without acute stage'
genetic material may integrate into host cell genome
44
give an example of a 'persistent slow infection'
HIV
45
describe 'transformation'
disruption of normal growth processes
46
give examples of normal growth provesses
EBV, HPV
47
how do transformed cells differ from healthy cells?
(in vitro) - greater saturation density - higher growth rate - loss of contact inhibition - appearance of 'new' cell surface antigens - indefinite growth
48
size of poliovirus
30nm
49
describe poliovirus structure
- ss + strand - non-enveloped - icosahedron - made up of 4 capsid proteins
50
describe the action of poliovirus
- replicates in cytoplasm - cytopathic (causes lysis) - infects gut and replicates in GALT - can infect and destroy motor neurones
51
describe the consequences of poliovirus
- asymptomatic mild infections in 99% of cases - meningitis - paralytic poliomyelitis (1:1000 of poliovirus infections in children)
52
herpes virus size
150 nm
53
herpes virus structure
- enveloped - icosahedron - 162 capsomeres
54
describe the action of herpes
- replicates in nucleus - cytopathic - infects epithelium, enters and ascends axons - establishes latent infection in neural ganglia - reactivation causes descent along same axons and replication in epithelium

Fundamentals of Medicine (1 decks)

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